Technical Field
Certain embodiments of the invention relate to a superconductive electromagnet and a charged particle beam therapy apparatus.
Description of Related Art
For example, a beam transport line for transporting a charged particle beam in the related art deflects the charged particle beam by causing a deflection electromagnet to generate a magnetic field in a beam duct through which the charged particle beam passes. In this case, it is necessary to allow uniform density of a magnetic flux in the beam duct inside the deflection electromagnet in order to accurately deflect the charged particle beam. Here, the related art discloses that a superconductive electromagnet is used as an electromagnet of the beam transport line in order to miniaturize the electromagnet while allowing the uniform density of the magnetic flux.
However, the superconductive electromagnet has a strong magnetomotive force. Consequently, in some cases, a magnetic pole arranged inside the electromagnet causes magnetic saturation. In this case, the density of the magnetic flux between magnetic poles becomes high particularly in the vicinity of a center position of the electromagnet, thereby degrading uniformity. In contrast, for example, it is also conceivable to realize uniform density of the magnetic flux is obtained by forming an irregular shape on an opposing surface of the magnetic pole. However, according to this method, an advantageous effect can be obtained for only the density of the magnetic flux having a specific size. Therefore, if the size varies in the density of the magnetic flux, the uniformity cannot be maintained.
It is desirable to provide a superconductive electromagnet and a charged particle beam therapy apparatus which can realize improved uniformity in density of a magnetic flux between magnetic poles.